Question

We currently have some php code that allows an end user to update records in our database by filling out a few fields on a form. The database has a field called sequentialNumber, and the user can enter a starting number and ending number, and an update query runs in the background on all records with a sequentialNumber between the starting and ending numbers. This is a pretty quick query.

We’ve been running into some problems lately where people are trying to update records that don’t exist. Now, this isn’t an issue on the database end, but they want to be notified if records don’t exist, and if so, which ones don’t exist.

The only way I can think of to do this is to run a select query in a loop:

for ($i=$startNum; $i<=$endNum; $i++)  {

 //run select query: select sequentialNumber from myTable where sequentialNumber = $startNum;

}

The problem is, our shared host has a timeout limit on scripts, and if the sequentialNumber batch is large enough, the script will time out. Is there a better way of checking for the existence of the records before running the update query?

EDIT:
It just occurred to me that I could do another kind of test: get the number of records they’re trying to update ($endNum – $startNum), and then do a count query:

select count(sequentialNumber) where sequentialNumber between $startNum and $endNum

If the result of the query is not the same as the value of the subtraction, then we know that all the records aren’t there. It wouldn’t be able to tell us WHICH ones aren’t there, but at least we’d know something wasn’t as expected. Is this a valid way to do things?

Answer 1

You could try

select sequentialNumber from myTable where sequentialNumber between $startNum and $endNum

This will return all known numbers in that range. Then you can use the array_search function to find out if a certain number is known or not. This should be faster than doing a lot of queries to the db.